Remove the binding of 'C-M-i' to 'ispell-complete-word' in Text mode.
Define a new 'ispell-completion-at-point' function and add that to
'completion-at-point-functions' in Text mode, such that
'completion-at-point' provides the same word completions as
'ispell-complete-word' does OOTB.

* lisp/textmodes/ispell.el (ispell-completion-at-point): New function.
* lisp/textmodes/text-mode.el (text-mode): Add it to 'c-a-p-functions'.
(text-mode-map): Remove 'C-M-i' binding.
(text-mode-meta-tab-ispell-complete-word): New user option.
* etc/NEWS: Announce it.
* doc/emacs/fixit.texi (Spelling)
* doc/emacs/text.texi (Text Mode)
* doc/lispref/modes.texi (Basic Major Modes)
(Example Major Modes): Update.
* lisp/mail/sendmail.el (mail-abbrevs-loaded)
* lisp/nxml/nxml-mode.el (nxml-mode-map): Remove superfluous binding.

32a32853ce9 Typofix in the doc/lispref/modes.texi
f98637b51b5 ; Fix 'add-face-text-property' shortdoc
3fff22eb20c Fix spell-checking email message with citations

* lisp/textmodes/tex-mode.el (tex-compile-commands): Respect
'tex-start-options' better.  (Bug#67030)

This became broken 7 years ago, when the 'boundp condition was
removed, and with it an important unrelated part of the code.
* lisp/textmodes/ispell.el (ispell-message): Fix cite-regexp.

Nested repetitions such as (A*)* potentially take exponential time but
can usually be rewritten in a faster and more readable way without
much trouble.  These were all found by Relint.

* lisp/obsolete/terminal.el (te-parse-program-and-args):
* lisp/org/org.el (org-make-tags-matcher):
Apply the transform (A+B*)+ -> A(A|B)*

* lisp/textmodes/fill.el (adaptive-fill-regexp):
Apply the transform A*(B+A*)* -> (A|B)*

* lisp/progmodes/idlw-shell.el (idlwave-shell-filter):
Find the last newline or CR in a more direct way.

* lisp/progmodes/vhdl-mode.el (vhdl-port-copy, vhdl-subprog-copy):
Trim trailing whitespace from a string in a more direct way.
All-whitespace strings are left unchanged as before.

* lisp/textmodes/dns-mode.el (dns-mode-syntax-table): Recognize
backslash as an escape character.  (Bug#66660)

(cherry picked from commit e6f05e189db73a0f0b29f987381ffef61a409232)

* lisp/textmodes/dns-mode.el (dns-mode-syntax-table): Fontify
quoted values correctly.  (Bug#62214)
Suggested by Trent W. Buck <trentbuck@gmail.com>.

(cherry picked from commit c586d984f279aa61de4f5dfc4f6df660188dd0f6)

* lisp/textmodes/dns-mode.el (dns-mode-syntax-table): Recognize
backslash as an escape character.  (Bug#66660)

* lisp/calendar/diary-lib.el (diary-display-function):
* lisp/calendar/icalendar.el (icalendar-export-alarms):
* lisp/emacs-lisp/elint.el (elint-ignored-warnings):
* lisp/mail/sendmail.el (send-mail-function):
* lisp/net/gnutls.el (gnutls-verify-error):
* lisp/gnus/mm-decode.el (mm-text-html-renderer):
* lisp/gnus/message.el (message-send-mail-function): Fix misplaced
defcustom :tags (bug#66196).
(message-tool-bar): Remove duplicate, overwritten, and nonexistent
defcustom :type gmm-tool-bar-list-item.
* lisp/progmodes/idlwave.el (idlwave-begin-line-comment): Strip
excessive defcustom :type quoting.
* lisp/progmodes/ps-mode.el (ps-mode-paper-size): Consolidate paper
sizes with same dimensions into a single defcustom menu entry.
* lisp/textmodes/glyphless-mode.el (glyphless-mode-types): Remove
duplicate defcustom :type choice.